Larvae of bloaters (Coregonus hoyi) were sampled systematically in southeastern Lake Michigan, off Saugatuck, Michigan, from 9 April to 22 April 1964; limited additional sampling was done on 15 October. All collections were made with a 1-m plankton net of 0.66-mm mesh. A standard series of samples consisted of oblique tows for each 10-fathom (sometimes 5-fathom) stratum over bottom depths from 5 to 50 fathoms by 5-fathom intervals. Some additional oblique tows were made at 60, 70, 80, and 88 fathoms, and a single day-night series of horizontal tows was made at 40 fathoms.
Few bloater larvae were taken when sampling began in early April. Numbers increased steadily thereafter until late June and early July, after which the catch declined rather rapidly. Few were caught on 22 August and none on 15 October. Hatching appeared to be at its peak about mid-June.
Approximately 83% of all bloater larvae were taken where the lake was between 40 and 60 fathoms deep. The depth of greatest abundance appeared to be between 50 and 60 fathoms. Larvae were present at all depths sampled except at 5 fathoms, but were scarce in areas 10, 15, and 20 fathoms deep. Most were found near bottom, except during the April and early May collections. About 96% were taken from strata in which the maximum temperature was not more than 4.7 C. There was evidence that weak swimming ability of the larvae as well as water temperature influenced vertical depth distribution. A limited but definite upward vertical migration occurred at night.
Additional publication details
Seasonal and depth distribution of larval bloaters (Coregonus hoyi) in southeastern Lake Michigan